Tons of road salt were spread on roadways in Maryland, Virginia and the District to help melt snow and ice this winter. Rain and melting snow washes all that salt down storm drains into rivers, streams and eventually into the Chesapeake Bay.

For example, the District applied 35,000 tons of salt by March 1, according to Linda Grant, spokeswoman for the D.C. Department of Public Works.

“The main impact we’re concerned about, with all the road salt, is actually in the fresh water parts of the Chesapeake Bay watershed, so the streams in your backyard,” says Dr. Beth McGee, water quality scientist for the Chesapeake Bay Foundation.

Scientists are concerned that road salt runoff could be harmful to watershed’s inhabitants.

“Salt can be toxic to fresh water organisms because they’re not used to dealing with that, they’re used to fresh water, not salty water and so the concentrations that they are seeing in some streams are approaching levels that we believe to be toxic. In other words we expose animals in a lab to these levels it can actually kill them or effect their growth,” McGee says.

The enormous amounts of road salt used this winter are not expected to harm the water quality of the Chesapeake Bay.

“The salinity in the bay will actually fluctuate seasonally, so in the spring it tends to be lower and as the summer proceeds it gets higher so the animals in the bay are used to tolerating changing levels of salt,” McGee says.

Another potential harmful impact of road salt can be found beneath our feet.

“Some of that (salt) is actually percolating down into groundwater,” McGee says pointing to a study in which she says scientists found elevated levels of salt in groundwater, not just in winter time but persisting throughout the year.